The present disclosure is related to a variable magnification optical system and an imaging apparatus. More particularly, the present disclosure is related to a variable magnification optical system which is favorably suited for use long distance surveillance cameras, and to an imaging apparatus equipped with the variable magnification optical system.
Conventionally, surveillance cameras are employed to prevent crime, to record scenes, etc., and the number thereof is increasing recently. Variable magnification optical systems are preferably utilized as lens systems for surveillance cameras in scenes that require high general use properties. Conventionally known variable magnification optical systems include the lens system which is disclosed in Japanese Unexamined Patent Publication No. 2011-133738. The lens system disclosed in Japanese Unexamined Patent Publication No. 2011-133738 is constituted by, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. In the lens system disclosed in Japanese Unexamined Patent Publication No. 2011-133738, the second lens group G2 and the fourth lens group G4 move when changing magnification.